It has been experimentally confirmed in a University of Toronto study]].[3] that human subjects observing the way others listened to people can predict the presence of the genetic variant.

In the study 23 couples were filmed describing a moment of personal suffering while their partner listened. Subjects then watched a 20 second silent recording of the exchange and scored the listener for their "prosocial traits", such as a nurturance or empathy.

The people with GG alleles were identifies to be more prosocial than people with the AG or AA variant. The effect was marked: of the top 10 most trusted people, 6 were GG; while of the 10 least trusted people, 9 had at least one copy of A.

↑Rodrigues SM, Saslow LR, Garcia N, John OP, Keltner D (December 2009). Oxytocin receptor genetic variation relates to empathy and stress reactivity in humans. Proceedings of the National Academy of Sciences of the United States of America106 (50): 21437–41.